CDF and DZero detectors move on to the next stage in upgrades for Run II.

by Mike Perricone

Tap the baton on the podium, get the orchestra's attention, and prepare to launch into a symphony such as you've never witnessed before.

Musical instruments usually range in size from a flute to a piano, with over a hundred instruments for a large symphony orchestra. The individual instruments playing this symphony at Fermilab can vary from a fiber detector smaller than the head of a pin--to a "moveable counting house" three stories tall and mounted on wheels, with cascades of thousands of miles of wire and cable running through and around the entire assembly. These instruments number close to a million, and they may be arriving from North or South America, Europe or Asia.

All these instruments and connections--and the new computer software to coordinate them--will come together to form Fermilab's two mammoth particle detectors, CDF and DZero, the 5,000-ton systems that will track and analyze the results of proton-antiproton collisions in the Tevatron when Run II begins in 2000.

"The activity in the detector will increase exponentially as we get close to the end of the year, with everyone trying to get their systems in and commissioned and running," said Mike Tuts, co-project manager for the DZero upgrade project. "The commissioning really will be like conducting an orchestra, trying to get everyone playing together--and playing the same song."

Planning for the detector upgrades began in 1990, and proceeded along with the experimental runs of the Tevatron and the Main Injector project. The first notes from particle collisions could appear sometime in the late summer and fall of 2000, as noted in the Department of Energy Lehman Reviews conducted for both detectors in mid-June.

With the new Main Injector and Antiproton Recycler combining with upgrades throughout Fermilab's accelerator complex, the beams of protons and antiprotons will reach new levels of intensity and will create 10 to 20 times more particle collisions than the Tevatron has ever before produced. Those new performance levels have seriously raised the stakes for the particle detectors poised to record hoped-for discoveries in new physics: the electronic systems will be recording more events in less time.

"The time between collisions at the Tevatron is getting a lot smaller," said Cathy Newman-Holmes, co-project manager for the CDF upgrade with Bob Kephart. "Formerly, the time between collisions was 3.5 microseconds. Now it's going to start off at 396 nanoseconds , and eventually we hope it will decrease to 132 nanoseconds.

"In other words," she continued, "it will be going from about 3,500 nanoseconds down to 132 nanoseconds. This dramatically shorter time between collisions means we have to make our trigger decisions much faster than before, determining which events we want to keep and which ones we don't."

At the heart of the data and tracking systems for both huge systems are new silicon microstrip detectors. They're being built at SiDet, the Fermilab Silicon Detector Facility, which DZero co-project manager Harry Weerts described as the "biggest silicon facility in the world."

These silicon vertex detectors, because of their design and the materials used, are highly resistant to damage from the particle beam and produce a high ratio of signal to noise. They will permit observations of what's going on very close to the particle collision point, almost like cranking up the power of a microscope.

"The proton-antiproton collisions may produce particles that don't live very long," Newman-Holmes explained. "These particles travel a short distance and then decay into other particles. With a silicon detector placed close to the interaction point, we are able to detect these very short-lived particles."

Both the CDF and DZero collaborations encompass experimenters and equipment from around the world in completing their upgrades. The silicon for the detectors comes from England, Japan and Russia; the fiber for the pinhead-sized readout devices (originally developed for military applications) comes from Japan, as does the superconducting magnet at DZero.

Also at DZero, several components are being supplied by institutions in Russia; they appear to be coming in on time despite the vagaries of the Russian economy. International politics have also come to bear on components provided by the Tata Institute in Bombay, India; the U.S. State Department prohibits Tata experimenters from coming to Fermilab because of India's atomic weapons tests last year. Fortunately, the components were delivered before the ban on visits, and other collaborators are trying to take up the slack for the installation. But the loss of Indian colleagues is being felt.

As hectic as the next stages of completion promise to be, they can also be seen as proof that the development stage has reached a satisfactory completion.

"Building a detector is not like building a car," Weerts said. "Everything we do has to be developed from scratch. When you start out, you're very uncertain of what you're doing. You're struggling and struggling, trying to make things work, solving one problem after another, and you know there are no guarantees.

"I think the Lehman review confirmed that we have everything in place. We have all the components. Now we have to put them together and make them run."

Newman-Holmes has to put an additional set of components into place. She is married to Steve Holmes, who was the project manager for the Main Injector from its inception. Coordinating schedules for themselves and their two children has been like conducting their own family symphony.

"Steve and I have really had to focus on making sure our children get picked up when they're supposed to be," she said. "There have been a few times when both of us showed up because we didn't know the other was going to be there. I'm happy to say there hasn't been a time when neither of us showed up."